Touch panels are electronic components functioning as position input devices. These are combined with display devices such as liquid crystal displays, and widely used in cellular phones, portable game machines, and the like. Touch panels are interfaces capable of, when an operator points a finger or an input pen at a specific position in the touch panel based on the display on a screen and the device senses information of the specific position, performing an appropriate operation that the operator wants. There are various types of touch panels according to principles of the operation of detecting the pointed-to position, and resistive or capacitive types are widely used. Particularly, the use of capacitive types has rapidly expanded mainly in mobile devices such as cellular phones. As for representative detection methods of the capacitive types, two methods, i.e., a surface type related to analog detection and a projection type by an integration detection method using an electrode on which patterning has been performed are exemplified.
As capacitive touch panels, touch panels provided with a glass plate having a conductive layer provided on one or both surfaces thereof (hereinafter, may be referred to as sensor glass) are used, and in general, a glass plate (hereinafter, may be referred to as cover glass) is laminated in front (touch surface side) of the sensor glass via an adhesive layer. In addition, a protective sheet is further stuck in front of the cover glass in order to prevent breakage of the cover glass and scattering of broken pieces.
As the protective sheet used for such purposes, protective sheets having a hard coating layer are used in many cases, since these have excellent scratch resistance. In addition, if desired, a layer having another function such as an antifouling function or an antireflection function is provided, or the hard coating layer is formed to have these functions (for example, PTLS 1 to 3).
In general, touch panels are attached to a front surface of a display unit using an adhesive. However, when the display unit has a particularly large size, only an outer edge of the touch panel may be fixed with an adhesive to another member such as a liquid crystal display due to cost considerations.
FIG. 9 shows a schematic cross-sectional view showing a configuration of a display device 200 with a capacitive touch panel, in which only an outer edge of a conventional capacitive touch panel is fixed to a front surface of the display unit via an adhesive. The display device 200 with a capacitive touch panel includes a liquid crystal display 210 having a polarizing plate 211 disposed on a top surface thereof, and a capacitive touch panel 220. The capacitive touch panel 220 includes a glass substrate 221, a conductive layer 222 provided in front of the glass substrate 221, a cover glass 224 laminated in front of the conductive layer 222 via an adhesive layer 223, and a protective sheet 227 laminated in front of the cover glass 224 via an adhesive layer 226, and a printing layer 225 is formed in an outer edge of the back surface of the cover glass 224. The capacitive touch panel 220 is disposed over a front surface of the liquid crystal display 210 such that a gap is provided between the capacitive touch panel 220 and the liquid crystal display 210, and its outer edge is fixed to the liquid crystal display 210 via an adhesive layer 230. Accordingly, a space is formed between the front surface of the liquid crystal display 210 and the back surface of the capacitive touch panel 220.
In optical film fields, when films, or a film and another member (for example, a glass plate) are brought into contact with each other, glare, Newton's rings, or blocking may occur. In order to prevent these phenomena, minute irregularities are provided on the surface of the film. The size of the irregularities to be formed is set according to performance to be requested (antiglare performance, anti-Newton ring performance, or antiblocking performance). In the case of the antiglare performance, the maximum size is set, and in the case of the antiblocking performance, the minimum size is set. As a method of forming such irregularities, a method of including particles in a hard coating layer is generally used (for example, PTLS 4 to 6).